The recovery of lysozyme from an aqueous solution containing precipitated lysozyme-AOT complexes formed by the direct addition of sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) to a lysozyme solution was studied using both solvents, and a counterionic surfactant. Ethanol, methanol and solvent mixtures dissolved the surfactant precipitate and recovered lysozyme as a solid. Recovery efficiency and protein stability varied with the type of solvent used. An entirely different method of recovery was also evaluated using a counterionic surfactant: trioctylmethylammonium chloride (TOMAC) which bound to AOT releasing lysozyme into solution. Complete recovery (100%) of lysozyme was achieved at a molar ratio of 2:1 (TOMAC:AOT), and the original protein activity was maintained in the final aqueous phase. The recovered lysozyme retained its secondary structure as observed in circular dichroism (CD) spectra. Specific activity studies show that counterionic surfactant extraction does not alter the biological activity of the enzyme. (C) 2011 American Institute of Chemical Engineers Biotechnol. Prog.,, 2011